1. Field of the Invention
The invention relates generally to an ammunition feeding device, and more particularly to such a device for feeding linked ammunition in timed sequence to the firing cycle of a self-loading firearm.
2. Description of Related Art
Firearms require a supply of ammunition. Small arms, including hand-carried rifles and pistols, often carry a small cache of ammunition in a magazine. Magazines are typically configured with an internal spring that helps move the top or lead cartridge stored in the magazine into a position where it may be loaded into the chamber by the action of the firearm. Many magazines hold between about 5-30 cartridges. Even when a magazine is configured to hold more than 30 cartridges, the limited number of available cartridges can be a drawback. Modern sporting rifles are capable of firing many rounds per minute, at which rates a magazine full of cartridges can be emptied in 2-3 seconds. There is a need in some situations to liberate a sporting rifle from the capacity limitations inherently imposed by standard magazines.
In addition to capacity limitations, traditional magazines can be cumbersome to load and unload. So-called “detachable” magazines, which are often regarded as more convenient than the “fixed” variety, are slow to load and can strain a user's thumbs when manually inserting one cartridge at a time. Various devices have been popularized to facilitate the magazine loading/unloading process, such as the popular Lula tool manufactured by maglula Ltd. of Rosh Ha'ayin Israel.
An alternative to magazine feed is belt feed. Belt feed systems overcome both the capacity limitation issues as well as the cumbersome loading/unloading issues of traditional magazines. Belt feed systems utilize ammunition cartridges that are linked together in a strip or so-called “belt”. In order to utilize belted ammunition, the firearm must be equipped with a mechanism that will advance cartridges in the belt one-at-a-time into the receiver so that the lead cartridge in the belt is stripped from the belt in synchronized movement with the cyclic action of the firearm during its feeding and chambering processes. As can be appreciated, the belt feeding device must function in time with the firing cycle of the firearm so that miss-feeds, jams and damage do not result. Belt feed systems are usually driven from energy harvested from gas pressure of a preceding fired cartridge. Mechanical couplings with the bolt, bolt-carrier or other reciprocating features of an auto-loading firearm assure synchronization between the advancement of cartridges and the firing cycle of the firearm.
Modern ammunition belts often contain cartridges clipped together in a flexible chain using metal links. These are sometimes referred to as disintegrating link ammunition because the lead link of the belt becomes disassociated from the remainder of the belt when the lead cartridge is stripped away. Examples of disintegrating link ammunition belts are generally shown at 20 in FIGS. 1 and 2. Cartridges in the belt 20 are indicated by reference number 22, except that features of the lead cartridge are identified by the given reference number with added suffix “A”. Links in the belt 20 are indicated by reference number 24, except that features of the lead link are identified by the given reference number with added suffix “A”. Each link 24 is designed to nest with the next adjacent link 24 while simultaneously gripping two adjacent cartridges 22.
Each link 24 includes a large central loop 26 formed as an open, or a semi-cylindrical, band dimensioned to fit snugly about the casing of a particular cartridge round 22. Front 28 and rear 30 loops flank the central loop 26 on opposite sides, both also formed as open, or semi-cylindrical, bands dimensioned to fit snugly about the casing of a next adjacent cartridge 22 and on opposite sides of the central loop of the next adjacent cartridge 22. The rear loop 30 includes a positioning finger 62 on one side which snaps into the extractor groove of the cartridge 22 to retain the cartridge 22 in proper feed alignment. The design of the link 24 permits a portion of the firearm bolt to ride through link loop openings and push cartridges 22 forward and out of the lead link 24A into the chamber for firing (as described subsequently in connection with FIGS. 10A and 10B).
Belt feed systems for the AR-15 platform, as one example, utilize highly customized upper receivers. This can be observed in firearms offered by the ARES Defense of Melbourne, Fla., as an example. In belt feed systems incorporated into the upper receiver, the bolt face encounters the lead round of ammunition 22A from below during the feeding and chambering processes. While effective in use, these prior art belt feed systems incorporated into the upper receiver preclude the use of standard replacement parts needed to maintain the upper receiver of the firearm.
For upper-receiver type belt feed systems for the AR-15 platform, it should be observed that the ammunition is always fed from left to right (as viewed by a user shouldering the firearm) with the link loops 26, 28, 30 oriented over the top of the cartridge 22 casings Ammunition belts are loaded into a machine gun equipped with an upper receiver feed mechanism so that the open sides of the link loops 26, 28, 30 are down. (Like that shown in FIG. 2.) Soldiers are sometimes taught to remember the phrase “keep the brass to the grass” to avoid loading a belt 20 upside down. As depicted in FIGS. 2 and 4, this universal feeding orientation for belted ammunition results in the leading end of the ammo belt 20 presenting empty front 28A and rear 30A loops of the lead link 24A. In use, disassociated links 24 exit the receiver through an ejection chute 34. See for example FIG. 4.
The fact that empty front 28A and rear 30A loops of the leading link 24A always extend beyond the lead cartridge 22A of the ammo belt 20 loaded in “brass to the grass” orientation (i.e., for an upper receiver type system) is significant. When the face of the firearm bolt strips the lead cartridge 22A during the feeding and chambering processes, tremendous pushing forces are created on the belt 20. Most prior art belt feed systems are designed so that the forward most edge of the front loop 28A of the leading link 24A is positioned directly against an inner wall 36 of the ejection chute 34. This condition is illustrated in FIG. 3. The forward most edge of the leading front loop 28A stabilizes the entire lead link 24A. The link 24 on the other side of the lead cartridge 22A is stabilized by the second-in-line cartridge 22. Thus, the forward most edge of the leading link 24A plays a crucial role in stabilizing the lead cartridge 22A as it is being fed and chambered by the bolt.
Belted ammunition 20 cannot be fed upside down into a traditional prior art upper-receiver type belt feed system. In the upside down condition, the bolt must encounter the lead cartridge 22A from above in order to strip it from the loop openings in the lead link 24A. Also, in the upside down condition an empty central loop 26A leads the ammo belt 20. (See FIG. 1.) The forward most edge of the central loop 26A cannot be used as a running surface against the inner wall 36 of the ejection chute 34 because in that case the chute 34 would not be wide enough to admit the remaining width of the lead link 24A (in particular its front loop 28A) after separating from the lead cartridge 22A.
In contrast, some prior art belt feed systems are integrated into the lower receivers. U.S. Pat. No. 3,035,495 to E. M. Stoner, granted May 22, 1962, discloses a belt feed system designed into the lower receiver portion of an AR-15 and capable of accommodating belted ammunition 20 fed upside down (i.e., like the orientation shown in FIGS. 3 and 5). In lower-receiver style belt feeding devices like this, the bolt face encounters the extractor rim of the lead cartridge 22A from above during the feeding and chambering processes, as typical with standard magazine feeding. Stoner accommodates the “upside down” orientation of the belted ammo 20 by incorporating a proprietary slot (not shown) in the central loop 26 of each link 24. A fin in the ejection chute 34 registers with the slot in the central loops 26 to resist stripping forces. Belt feed systems that are integrated into the lower receivers (i.e., operating on the 1962 E. M. Stoner design depicted in U.S. Pat. No. 3,035,495) are disfavored due to the required use of non-mil spec links. Such non-standard links preclude the easy acquisition of belted ammunition on the open market, and are more expensive to manufacture than traditional military-style links 24.
There is therefore a need in the art for an improved belt feeding device that is integrated into the lower receiver but does not require proprietary linked ammunition and that attains the robust operating performance of an upper-receiver type feeding device.